1. Field of Invention
The present invention relates to a video processing apparatus and a video processing method. More particularly, the present invention relates to a video processing apparatus and a video processing method which can reduce the effects of noise and enhance fineness of an image.
2. Description of the Related Art
A video processing apparatus, such as a television, receives a video signal from a broadcasting station containing specific video according to a digital television broadcasting signal, cable television broadcasting signal, and the like. The video processing apparatus performs a video-process for the received video signal and then outputs an image. The video processing apparatus also receives a video signal from various video equipment, such as, a video cassette recorder (VCR), a digital versatile disk (DVD) player, and the like. Then the video processing apparatus performs a video process for the received video signal.
The video signal received by such video processing apparatus is a frequency signal corresponding to a characteristic of the image. For example, an area in which the image is not change corresponds to a low frequency, and an area (such as a corner) in which the image is rapidly changed corresponds to a high frequency. On the other hand, a usable frequency band for the video signal received by the video processing apparatus is limited in order to enhance an efficiency of the frequency resource. For example, in a television system of the National Television System Committee, a frequency band width assigned to one channel is 6 MHz. In this frequency band width, a frequency given for expressing an image is 4.2 MHz.
However, an original image has various frequency components, such as an image which is expressed by the high frequency of 4.2 MHz or more. In this case, once the original image, having a frequency component of 4.2 MHz or more, is converted into a video signal, the frequency components are lost. As a result, problems may exist in which an area, such as a corner of the image, is not displayed clearly, and an unstable phenomenon, such as ringing, in which the image is oscillated, is generated.
In order to solve the phenomenon such as the ringing and the like, the coring process for the video signal has been conventionally suggested.
FIG. 1 is a block diagram schematically showing a structure of a coring processing unit of a conventional video processing apparatus 1. The video processing apparatus 1 of FIG. 1 is provided with a high-pass filter 11 for generating input high frequency components of an input video signal, a first mixer 12 for eliminating the high frequency component filtered by the high pass filter 11 from the input video signal and outputting a low frequency component; a coring unit 13 for performing a coring process for the high frequency component filtered by the high pass filter 11 and inputted thereto; and a second mixer 14 for adding the signal output from the coring unit 13 to the low frequency component output from the first mixer 12; and then outputting the added signal.
The coring unit 13 eliminates an unnecessary component (that is, a noise component) in the high frequency components. FIG. 2 is a graph showing a gain 15 that represents a ratio of a level of an output signal to a level of an input signal of the coring unit 13. As shown in FIG. 2, the coring unit 13 sets the gain of input signal, having a level (−a˜a) below a certain range, to 0 (zero), and then eliminates the unnecessary components and outputs the signal. The coring unit 13 eliminates a section with a low signal level from the high frequency component, which causes the ringing phenomenon in the video signal, and attenuates the ringing phenomenon.
However, since the signal eliminated in the coring unit 13 comprises noise, as well as image information, the higher a threshold level (a or −a) is for preventing the ringing, the more image information is lost. Accordingly, although the ringing phenomenon is improved, a problem exists in which fineness of the image decreases.
Accordingly, there is a need for an improved video processing apparatus and video processing method that reduces noise in a video signal without decreasing fineness of an image.